Apparatus and method for recovering liquid droplets in immersion lithography

ABSTRACT

Immersion fluid remaining on a portion of a substrate after that portion has passed an immersion nozzle is removed by moving the substrate relative to an immersion nozzle so that the portion of the substrate on which the immersion fluid remains is passed by the immersion nozzle again. A path is determined along which the substrate is to be moved to remove the remaining immersion fluid. The path can be determined based upon previous movements of the substrate, including factors such as the speed and/or length of the previous movements. Alternatively, portions of the substrate on which immersion fluid remains can be detected, and then the substrate can be moved so that the portion of the substrate on which the immersion fluid remains is passed by the immersion nozzle based on the results of the detection. Immersion fluid also can be removed from the stage surface located beyond the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/728,313 filed Oct. 20, 2005, the disclosure of whichis incorporated herein by reference in its entirety.

BACKGROUND

The invention relates generally to immersion lithography apparatus andmethods, and particularly to apparatus and methods for recoveringdroplets of immersion liquid that have been left on a substrate duringimmersion lithography.

Lithography exposure apparatus are commonly used to transfer images froma reticle onto a semiconductor wafer during semiconductor processing. Atypical exposure apparatus includes an illumination source, a reticlestage assembly that positions a reticle containing one or more patterns,a projection system, a wafer stage assembly that positions asemiconductor wafer, and a measurement system that precisely monitorsthe positions of the reticle and the wafer. As is known, lithographyexposure apparatus also can be used to form images on substrates otherthan semiconductor wafers, for example, glass or quartz substrates inorder to form, for example, flat panel displays such as LCD displays.

Immersion lithography is a technique that can enhance the resolution oflithography exposure apparatus by permitting exposure to take place witha numerical aperture (NA) that is greater than the NA that can beachieved in conventional “dry” lithography exposure apparatus. Byfilling the space between the final optical element of the projectionsystem and the resist-coated target (wafer or other substrate) withimmersion fluid, immersion lithography permits exposure with light thatwould otherwise be internally reflected at an optic-air interface.Numerical apertures as high as the index of the immersion fluid (or ofthe resist or lens material, whichever is least) are possible inimmersion lithography systems. Liquid immersion also increases the waferdepth-of-focus, that is, the tolerable error in the vertical position ofthe wafer, by the index of the immersion fluid compared to a dry systemhaving the same numerical aperture. Immersion lithography thus has thepotential to improve resolution enhancement equivalent to a shift from193 nm to 157 nm without actually decreasing the exposure lightwavelength. Thus, unlike a shift in the exposure light wavelength, theuse of immersion would not require the development of new light sources,optical materials (for the illumination and projection systems) orcoatings, and should allow the use of the same or similar resists asconventional “dry” lithography at the same wavelength. In an immersionsystem in which only the final optical element of the projection systemand its housing and the wafer (and perhaps portions of the stage aswell) are in contact with the immersion fluid, much of the technologyand design developed for dry lithography can carry over directly toimmersion lithography.

However, because the wafer (or other substrate) moves rapidly in atypical lithography system, some of the immersion fluid in the immersionarea between the projection system and the substrate tends to be carriedaway from the immersion area. If the immersion fluid escapes from theimmersion area, that fluid can interfere with operation of othercomponents of the lithography system. One way to prevent the immersionfluid from carrying away from the immersion area is described in WO2005/24517, which corresponds to U.S. patent application Ser. No.11/362,833, the disclosure of which is incorporated herein by referencein its entirety. This document discloses an immersion fluid supply andrecovery system in which a porous member surrounds the immersion areaand is in fluid communication with the space that defines the immersionarea. The porous member is maintained at a pressure that is under thebubble point of the porous member, whereby immersion fluid that escapesfrom the immersion area is captured (recovered) by the porous member.

Other fluid recovery and fluid containment systems have been described.For example, in one such system described in US-2004/0165159-A1, theimmersion liquid is maintained in the immersion area by forming an “aircurtain” around the immersion area by supplying pressurized gas to thearea surrounding the immersion area.

However, even when there is a satisfactory fluid recovery/containmentsystem, droplets of immersion liquid can be left on portions of thesubstrate after the portion of the substrate has passed beneath theprojection system and the underlying immersion area. Such droplets causelocal cooling of the wafer and the environment around the wafer when thedroplets evaporate, which can have an undesirable effect on the exposureoperation. For example, evaporation of the droplets can change therefractive index in the optical path of the detecting light used by thelithography apparatus interferometer(s), and thus adversely affect themeasurements made during the exposure operation. Evaporation of thedroplets also can leave an area of contamination on the wafer.Furthermore, subsequent high acceleration movements of the substrate cancause droplets to be scattered to surrounding components of thelithography apparatus, causing those components to corrode or at leastfouling those components.

WO 2005/020299 and its related US 2006/0139593 A1 disclose an immersionlithography apparatus that moves the substrate relative to an immersionfluid supply/recovery nozzle after the entire substrate has been exposedin order to remove any immersion fluid that may remain on the substrate.

SUMMARY

According to aspects of the invention, immersion fluid that remains on aportion of a substrate is removed from the portion of the substrate bymoving the substrate. The immersion fluid that remained on the substratecan be removed by a fluid recovery system. Immersion fluid also can beremoved from the stage surface.

According to a preferred embodiment, the substrate is moved so that theportion of the substrate on which the fluid may remain is returned tothe immersion area so that the remaining immersion fluid is engulfed bythe immersion fluid that is located in the immersion area.

According to one embodiment, a path is determined along which thesubstrate is to be moved so as to remove the remaining immersion fluid.For example, the path can be determined based upon previous movements ofthe substrate. The path can be determined based on positionalinformation about the area on the substrate where the droplets arelikely to remain. Factors that can be taken into account include thespeed and length of the previous movements of the substrate.

According to another embodiment, portions of the substrate on whichimmersion fluid remains can be detected, and then the substrate can bemoved based on the results of the detection to remove the remainingimmersion fluid. The detection can be made by an optical detector suchas, for example, the auto-focus detector already existing in manyimmersion lithography apparatus.

As is known, a typical exposure operation forms an image of a patternonto a plurality of shot areas on a substrate. In accordance withaspects of the invention, the substrate can be moved so as to removeimmersion liquid remaining on the substrate at least once between astart time when exposure of a first one of the shot areas on thesubstrate begins and an end time after the exposure of a last one of theshot areas on the substrate has been completed. According to someembodiments, the remaining immersion fluid removal step can be performedmultiple times between the start time and the end time of exposure onthe substrate. According to some embodiments, the removal step isperformed at least after the exposure of all the shot areas on thesubstrate has been completed.

According to an aspect of the invention, an immersion lithographyapparatus that includes a projection system and a substrate stage thatholds a substrate and moves the substrate relative to the projectionsystem, further includes a controller that moves the substrate stage sothat the immersion fluid that remains on the portion of the substrate isremoved. As noted above, the controller controls the movement of thesubstrate based upon determinations that can be made regarding portionsof the substrate where immersion fluid is likely to remain and/or basedupon actual detection of immersion fluid that remains on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings of exemplary embodiments in which like reference numeralsdesignate like elements, and in which:

FIG. 1 is a simplified elevational view schematically illustrating animmersion lithography system according to an embodiment of theinvention;

FIG. 2 is a perspective view of a nozzle for fluid delivery and recoverythat can be used with the invention;

FIGS. 3A and 3B illustrate removal of an immersion fluid droplet from asubstrate;

FIG. 4 is a flowchart showing some basic steps performed according tosome aspects of the invention when removing immersion fluid that remainson a substrate;

FIG. 5 is a schematic diagram showing an embodiment in which thelocation(s) of remaining immersion fluid is/are detected using anauto-focus detector of the immersion lithography apparatus;

FIG. 6 shows one example of the movement path of a substrate so as toexpose the shot areas on the substrate;

FIG. 7A is a flowchart that outlines a process for manufacturing adevice in accordance with aspects of the invention; and

FIG. 7B is a flowchart that outlines device processing in more detail.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows an immersion lithography system 10 including a reticlestage 12 on which a reticle is supported, a projection system 14, and awafer 16 supported on a wafer stage 18. An immersion fluid supply andrecovery apparatus 100, which is sometimes referred to herein as animmersion fluid supply and recovery nozzle, is disposed around the finaloptical element 22 of the projection system 14 so as to provide andrecover an immersion fluid, which may be a liquid such as, for example,water between the final optical element 22 and the wafer 16 during anexposure operation. In the present embodiment, the immersion lithographysystem 10 is a scanning lithography system in which the reticle and thewafer 16 are moved synchronously in respective scanning directionsduring an exposure operation.

The illumination source of the lithography system can be a light sourcesuch as, for example, a mercury g-line source (436 nm) or i-line source(365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm) ora F₂ laser (157 nm). The projection system 14 projects and/or focusesthe light passing through the reticle onto the wafer 16. Depending uponthe design of the exposure apparatus, the projection system 14 canmagnify or reduce the image illuminated on the reticle. It also could bea 1× magnification system.

When far ultra-violet radiation such as from the excimer laser is used,glass materials such as quartz and fluorite that transmit farultra-violet rays can be used in the projection system 14. Theprojection system 14 can be catadioptric, refractive or completelyreflective.

With an exposure device that employs radiation of wavelength 200 nm orlower, use of the catadioptric type optical system can be considered.Examples of the catadioptric type of optical system are shown in U.S.Pat. No. 5,668,672 and U.S. Pat. No. 5,835,275. In these cases, thereflecting optical device can be a catadioptric optical systemincorporating a beam splitter and concave mirror. U.S. Pat. No.5,689,377 also uses a reflecting-refracting type of optical systemincorporating a concave mirror, etc., but without a beam splitter, andcan also be employed with this invention. The disclosures of theabove-mentioned U.S. patents are incorporated herein by reference intheir entireties.

FIG. 2 is a perspective view of one embodiment of an immersion fluidsupply and recovery nozzle 100 according to aspects of the invention.Further details of the immersion fluid supply and recovery nozzle 100are described in U.S. patent application Ser. No. 11/443,361 filed May31, 2006. The disclosure of U.S. patent application Ser. No. 11/443,361is incorporated herein by reference in its entirety. As is generallyknown from the above-incorporated WO 2005/24517 (and corresponding U.S.patent application Ser. No. 11/362,833), the nozzle 100 includes ahousing or manifold portion 120 and a porous member 110. The housing 120includes various passages through which immersion fluid is supplied toand conveyed away from the gap that includes at least a space betweenthe final optical element 22 of the projection system 14 and thesubstrate (e.g., wafer 16) that is the object of exposure duringexposure.

As can be appreciated from FIG. 1, the nozzle 100 encircles the finaloptical element 22 of the projection system 14. Because the illustratedembodiment is a scanning exposure apparatus in which the reticle and thesubstrate are synchronously moved relative to the projection system 14during exposure, a generally slit-shaped irradiation area is projectedthrough the reticle, projection system 14 and onto the substrate 16.Accordingly, the lower portion of the housing 120 includes a slit-shaped(or rectangular) opening 128. The irradiation beam passes through theopening 128 during exposure. When fully assembled, the porous member 110encircles the opening 128, as can be seen in FIG. 2. The immersion areais formed in the gap between the final optical element 22 of theprojection system 14 and the upper surface of the substrate (e.g., wafer16). The immersion area is also formed in the gap between the lowersurface surrounding the opening 128 of the housing 120 and the uppersurface of the substrate. The immersion area generally is located in thearea of the opening 128 and the area surrounding the opening 128 betweenthe opening and the inner perimeter of the porous member 110. Asdescribed below, immersion fluid such as water is supplied through thehousing 120 to the immersion area and is maintained in the immersionarea during exposure. As the substrate moves below the projection system14 and nozzle 100, the porous member 110 that surrounds the immersionarea prevents immersion fluid from escaping from the area below thenozzle 100.

The surface of the porous member 110 that faces the wafer 16 (that is,the lower surface of the porous member 110) can be flat or tapered. Inthe illustrated embodiment, the porous member 110 tapers upwardly fromits center toward its radial outer edges. Thus, when positioned adjacentto the wafer 16, the central portion of the porous member 110 (theportion adjacent to central opening 114) is located closer to the wafer16 than the radially outer edges of the porous member 110.

The porous member 110 may be a mesh or may be formed of a porousmaterial having holes typically with a size smaller than 150 microns.For example, the porous member 110 may be a wire mesh including wovenpieces or layers of material made of metal, plastic, or the like, aporous metal, a porous glass, a porous plastic, a porous ceramic, or asheet of material having chemically etched holes (for example, byphoto-etching).

The invention can be used with other immersion nozzle architectures, forexample, the invention can be used with immersion nozzles that do notinclude a porous member, such as the nozzle disclosed in the previouslymentioned WO 2005/020299 and its related US 2006/0139593 A1. Thedisclosures of WO 2005/020299 and US 2006/0139593 A1 are incorporatedherein by reference in their entireties.

FIGS. 3A and 3B illustrate removal of an immersion fluid droplet 32 fromthe surface of a substrate 16, such as a silicon wafer. These figuresshow a plan view of the substrate 16 with an immersion fluid droplet 32located on the upper surface of the substrate 16. The outer perimeter ofthe immersion nozzle 100 is shown to be spaced from the immersion area110. The substrate is moved in the direction of the arrow shown in FIG.3B so that the immersion fluid droplet 32 that remained on the substratesurface is engulfed by the immersion area 110. Once the droplet 32 isengulfed by the immersion area 110, it can be removed from the surfaceof the substrate 16.

The invention also can be used to remove fluid droplets that remain onthe upper surface of the substrate stage 18 surrounding the substrate16. As is known, when shot areas in the vicinity of the outer perimeterof the substrate 16 are exposed, at least part of the immersion area 110can extend beyond the outer perimeter of the substrate 16, and thusimmersion fluid from the immersion area 110 can flow onto the uppersurface of the substrate stage 18 at these locations. Such immersionfluid sometimes is left on the substrate stage upper surface (i.e., itis not removed by the immersion nozzle 100) due to, for example, thespeed at which the substrate stage is moving when these areas areexposed. The invention can be used to remove any remaining immersionfluid from the upper surface of the substrate stage 18.

FIG. 4 is a simplified flowchart showing basic steps for implementingaspects of the invention. These steps can be implemented by theimmersion lithography apparatus controller 200 illustrated in FIG. 5. Inaccordance with step S1, a determination is made regarding the one ormore locations where fluid remains on the substrate (and/or substratestage) surface. As will be described in more detail below, thedetermination can be based on detecting actual locations of remainingimmersion fluid or it can be made by determining locations whereimmersion fluid is likely to remain based upon previous motions of thesubstrate. After the one or more locations are determined, then in stepS2, the substrate is moved so that the immersion nozzle is positionedadjacent to the location(s) where immersion fluid is, or is believed tobe, located. Thus, a remaining immersion fluid removal path isdetermined, and then the substrate 16 is moved along the path so thatthe substrate is positioned relative to the immersion nozzle 100.Preferably, the substrate is moved so that the immersion area 110 belowthe immersion fluid nozzle 100 will touch, and thereby engulf, theimmersion fluid droplets (or other forms of remaining immersion fluid)present on the substrate and/or substrate stage upper surface. As shownin step S3, the remaining immersion fluid is removed through theimmersion nozzle 100 once it is positioned so that the remainingimmersion fluid is engulfed by the immersion area 110.

FIG. 5 shows one arrangement whereby the location of any remainingimmersion fluid is detected. A detector, such as an optical detector, isused to detect where immersion fluid remains on the substrate after atleast one of the shot areas on the substrate has been exposed with apattern of an image. In this embodiment, the optical detector used inFIG. 5 is the auto-focus system already existing in immersionlithography apparatus. The auto-focus system includes a light emittingelement 160 a and a light detecting element 160 b. The light emittingelement 160 a emits one or more beams of light at an oblique anglerelative to the substrate upper surface. This light beam is reflected bythe upper surface and then detected by the light detector 160 b. Thelight path of the detecting light is identified with reference numeral162 in FIG. 5.

The auto-focus detector can be arranged so that it projects its lightbeam at an area adjacent to the immersion area, and thus it can detectwhether any droplets are present on portions of the substrate thatshould be dry. Thus, for example, by moving the substrate after all orsome shot areas of the substrate have been exposed with the imagepattern, the auto-focus detector can be used to determine whether anyimmersion fluid remains on the substrate surface. A path then can bedetermined for moving the substrate so that the remaining immersionfluid is engulfed by the immersion area 110 below the immersion nozzle100, and thereby removed from the substrate.

FIG. 6 illustrates a plurality of shot areas S1-S28 disposed on theupper surface of the substrate 16. The line 180 denotes the path thatthe substrate follows in order to expose the shot areas from shot areaS1 to shot area S28. According to another aspect of the invention, thepath can be used to determine locations on the substrate where immersionfluid likely remains after one or more of the shot areas have beenexposed with the pattern image. For example, it can be determined thatimmersion fluid likely remains on portions of the substrate where thesubstrate was moved at higher speeds, or subjected to higheraccelerations (which occur at locations where the movement direction ofthe substrate is changed such as at the curved portions of the path180). Based on such movements, the substrate can be controlled to returnthe portions of the substrate that likely have remaining immersion fluidback below the immersion nozzle 100 so that the remaining immersionfluid is removed.

The procedure in which the substrate is moved so that locations likelyto contain remaining immersion fluid are again passed below theimmersion nozzle 100 can take place after all shot areas have beenexposed or can take place intermittently during exposure of the shotareas. For example, it may not be desirable to wait until all shot areashave been exposed because fluid remaining on the substrate from theexposure of previous shot areas may be scattered from the substrate ormay evaporate before exposure of all shot areas is completed. Thus, itmay be desirable to move the substrate so that fluid that remains on thesubstrate is removed shortly after it is likely that such immersionfluid has been left on the substrate. For example, referring to FIG. 6,since it is likely that immersion fluid remains in the area between shotareas S2 and S3, it may be desirable to move the substrate to removesuch remaining immersion fluid after shot area S14 has been exposed withthe pattern image. Similarly, because immersion fluid likely remains onthe substrate along the path 180 between shot areas S8 and S9, it wouldbe desirable to move the substrate so as to remove such immersion fluidafter exposure of shot area S20. The path along which the substrate ismoved also can be determined so as to maximize throughput.

There are a number of different types of lithographic apparatus, andalthough the illustrated embodiment is a scanning exposure apparatus,the invention also can be used with step-and-repeat typephotolithography apparatus that expose the pattern from the reticle ontothe substrate while the reticle and the substrate are stationary. In thestep and repeat process, the substrate is in a constant positionrelative to the reticle and the projection system during the exposure ofan individual field (shot area). Subsequently, between consecutiveexposure steps, the substrate is consecutively moved with a substratestage assembly perpendicularly to the optical axis of the projectionsystem so that the next shot area of the substrate is brought intoposition relative to the projection system and the reticle for exposure.Following this process, the images on the reticle are sequentiallyexposed onto the shot areas of the substrate, and then the next shotarea of the substrate is brought into position relative to theprojection system and the reticle.

The use of the exposure apparatus described herein is not limited to aphotolithography system for semiconductor manufacturing. The exposureapparatus, for example, can be used as an LCD photolithography systemthat exposes a liquid crystal display device pattern onto a rectangularglass plate or a photolithography system for manufacturing a thin filmmagnetic head.

Semiconductor devices can be fabricated using the above describedsystems, by the process shown generally in FIG. 7A. In step 801 thedevice's function and performance characteristics are designed. Next, instep 802, a mask (reticle) having a pattern is designed according to theprevious designing step, and in a step 803 a wafer is made from asilicon material. The mask pattern designed in step 802 is exposed ontothe wafer from step 803 in step 804 by a photolithography systemdescribed hereinabove in accordance with the invention. In step 805 thesemiconductor device is assembled (including the dicing process, bondingprocess and packaging process). Finally, the device is then inspected instep 806.

FIG. 7B illustrates a detailed flowchart example of the above-mentionedstep 804 in the case of fabricating semiconductor devices. In FIG. 7B,in step 811 (oxidation step), the wafer surface is oxidized. In step 812(CVD step), an insulation film is formed on the wafer surface. In step813 (electrode formation step), electrodes are formed on the wafer byvapor deposition. In step 814 (ion implantation step), ions areimplanted in the wafer. The above mentioned steps 811-814 form thepreprocessing steps for wafers during wafer processing, and selection ismade at each step according to processing requirements.

At each stage of wafer processing, when the above-mentionedpreprocessing steps have been completed, the following post-processingsteps are implemented. During post-processing, first, in step 815(photoresist formation step), photoresist is applied to a wafer. Next,in step 816 (exposure step), the above-mentioned exposure device is usedto transfer the circuit pattern of a mask (reticle) to a wafer. Then instep 817 (developing step), the exposed wafer is developed, and in step818 (etching step), parts other than residual photoresist (exposedmaterial surface) are removed by etching. In step 819 (photoresistremoval step), unnecessary photoresist remaining after etching isremoved. Multiple circuit patterns are formed by repetition of thesepreprocessing and post-processing steps.

A photolithography system (an exposure apparatus) according to theembodiments described herein can be built by assembling varioussubsystems in such a manner that prescribed mechanical accuracy,electrical accuracy, and optical accuracy are maintained. In order tomaintain the various accuracies, prior to and following assembly, everyoptical system is adjusted to achieve its optical accuracy. Similarly,every mechanical system and every electrical system are adjusted toachieve their respective mechanical and electrical accuracies. Theprocess of assembling each subsystem into a photolithography systemincludes providing mechanical interfaces, electrical circuit wiringconnections and air pressure plumbing connections between eachsubsystem. Each subsystem also is assembled prior to assembling aphotolithography system from the various subsystems. Once aphotolithography system is assembled using the various subsystems, atotal adjustment is performed to make sure that accuracy is maintainedin the complete photolithography system. Additionally, it is desirableto manufacture an exposure system in a clean room where the temperatureand cleanliness are controlled.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments or constructions. The-invention isintended to cover various modifications and equivalent arrangements. Inaddition, while the various elements of the preferred embodiments areshown in various combinations and configurations, that are exemplary,other combinations and configurations, including more, less or only asingle element, are also within the spirit and scope of the invention.

1. A method of removing immersion fluid that remains on a portion of asubstrate after the portion of the substrate has passed by an immersionarea in an immersion lithography apparatus, the method comprising:detecting the portion of the substrate on which the immersion fluidremains; and based on results of the detecting step, moving thesubstrate to remove the immersion fluid that remains on the portion ofthe substrate.
 2. The method of claim 1, wherein the substrate is movedrelative to the immersion area based on results of the detecting step sothat the immersion fluid that remains on the portion of the substrate isengulfed by the immersion fluid of the immersion area.
 3. The method ofclaim 2, wherein the immersion lithography apparatus has a fluidrecovery system, and the substrate is moved relative to the fluidrecovery system based on results of the detecting step so that theimmersion fluid that remains on the portion of the substrate is removedthrough the fluid recovery system.
 4. The method of claim 1, wherein thedetecting step includes optically detecting the portion of the substrateon which the immersion fluid remains.
 5. The method of claim 4, whereinthe detecting step is performed using an auto-focus detector.
 6. Themethod of claim 1, wherein the immersion fluid that remains on thesubstrate is in the form of droplets.
 7. The method of claim 1, whereina plurality of shot areas on the substrate are exposed, and the movingstep is performed at least once between a start time when exposure of afirst one of the shot areas on the substrate begins and an end timeafter the exposure of a last one of the shot areas on the substrate hasbeen completed.
 8. The method of claim 7, wherein the moving step isperformed multiple times between the start time and the end time.
 9. Themethod of claim 7, wherein the moving step is performed at least afterthe exposure of all the shot areas on the substrate has been completed.10. The method of claim 1, wherein the method further includes removingimmersion fluid that remains on a surface of a stage on which thesubstrate is mounted, the surface being disposed beyond a periphery ofthe substrate.
 11. A method of removing immersion fluid that remains ona portion of a substrate after the portion of the substrate has passedby an immersion area in an immersion lithography apparatus, the methodcomprising: determining a path along which the substrate is to be moved,the path being determined based upon previous movement of the substrate;and moving the substrate based on the determined path to remove theimmersion fluid that remains on the portion of the substrate.
 12. Themethod of claim 11, wherein the path is determined based upon at leastone of a speed and a length of the previous movements of the substrate.13. The method of claim 1 1, wherein the substrate is moved relative tothe immersion area based on the determined path so that the immersionfluid that remains on the portion of the substrate is engulfed by theimmersion fluid of the immersion area.
 14. The method of claim 13,wherein the immersion lithography apparatus has a fluid recovery system,and the substrate is moved relative to the fluid recovery system basedon the determined path so that the immersion fluid that remains on theportion of the substrate is removed through the fluid recovery system.15. The method of claim 11, wherein the immersion fluid that remains onthe substrate is in the form of droplets.
 16. The method of claim 11,wherein a plurality of shot areas on the substrate are exposed, and themoving step is performed at least once between a start time whenexposure of a first one of the shot areas on the substrate begins and anend time after the exposure of a last one of the shot areas on thesubstrate has been completed.
 17. The method of claim 16, wherein themoving step is performed multiple times between the start time and theend time.
 18. The method of claim 16, wherein the moving step isperformed at least after the exposure of all the shot areas on thesubstrate has been completed.
 19. The method of claim 11, wherein themethod further includes removing immersion fluid that remains on asurface of a stage on which the substrate is mounted, the surface beingdisposed beyond a periphery of the substrate.
 20. A method of performingimmersion lithography with an immersion lithography apparatus, themethod comprising: exposing a substrate with radiation through aprojection system and through an immersion fluid that forms an immersionarea adjacent to the projection system; detecting a portion of thesubstrate on which the immersion fluid remains; and based on results ofthe detecting step, moving the substrate to remove the immersion fluidthat remains on the portion of the substrate.
 21. The method of claim20, wherein the substrate is moved relative to the immersion area basedon results of the detecting step so that the immersion fluid thatremains on the substrate is engulfed by the immersion fluid of theimmersion area.
 22. The method of claim 21, wherein the immersionlithography apparatus has a fluid recovery system, and the substrate ismoved relative to the fluid recovery system based on results of thedetecting step so that the immersion fluid that remains on the portionof the substrate is removed through the fluid recovery system.
 23. Themethod of claim 20, wherein the detecting step includes opticallydetecting the portion of the substrate on which the immersion fluidremains.
 24. The method of claim 23, wherein the detecting step isperformed using an auto-focus detector.
 25. The method of claim 20,wherein the immersion fluid that remains on the substrate is in the formof droplets.
 26. The method of claim 20, wherein a plurality of shotareas on the substrate are exposed through the projection system, andthe moving step is performed at least once between a start time whenexposure of a first one of the shot areas on the substrate begins and anend time after the exposure of a last one of the shot areas on thesubstrate has been completed.
 27. The method of claim 26, wherein themoving step is performed multiple times between the start time and theend time.
 28. The method of claim 26, wherein the moving step isperformed at least after the exposure of all the shot areas on thesubstrate has been completed.
 29. The method of claim 20, wherein theimmersion lithography apparatus is a scanning exposure apparatus thatmoves the substrate relative to the immersion area in a scanningdirection during the exposing step.
 30. The method of claim 20, whereinthe method further includes removing immersion fluid that remains on asurface of a stage on which the substrate is mounted, the surface beingdisposed beyond a periphery of the substrate.
 31. A method of performingimmersion lithography with an immersion lithography apparatus, themethod comprising: exposing a substrate with radiation through aprojection system and through an immersion fluid that forms an immersionarea adjacent to the projection system; determining a path along whichthe substrate is to be moved, the path being determined based uponprevious movement of the substrate; and based on the determined path,moving the substrate to remove the immersion fluid that remains on theportion of the substrate.
 32. The method of claim 31, wherein the pathis determined based upon at least one of a speed and a length of theprevious movements of the substrate.
 33. The method of claim 31, whereinthe substrate is moved relative to the immersion area based on thedetermined path so that the immersion fluid that remains on thesubstrate is engulfed by the immersion fluid of the immersion area. 34.The method of claim 33, wherein the immersion lithography apparatus hasa fluid recovery system, and the substrate is moved relative to thefluid recovery system based on the determined path so that the immersionfluid that remains on the portion of the substrate is removed throughthe fluid recovery system.
 35. The method of claim 31, wherein theimmersion fluid that remains on the substrate is in the form ofdroplets.
 36. The method of claim 31, wherein a plurality of shot areason the substrate are exposed through the projection system, and themoving step is performed at least once between a start time whenexposure of a first one of the shot areas on the substrate begins and anend time after the exposure of a last one of the shot areas on thesubstrate has been completed.
 37. The method of claim 36, wherein themoving step is performed multiple times between the start time and theend time.
 38. The method of claim 36, wherein the moving step isperformed at least after the exposure of all the shot areas on thesubstrate has been completed.
 39. The method of claim 31, wherein theimmersion lithography apparatus is a scanning exposure apparatus thatmoves the substrate relative to the immersion area in a scanningdirection during the exposing step.
 40. The method of claim 31, whereinthe method further includes removing immersion fluid that remains on asurface of a stage on which the substrate is mounted, the surface beingdisposed beyond a periphery of the substrate.
 41. An immersionlithography apparatus comprising: a projection system that exposes asubstrate with radiation, the substrate being exposed with the radiationthrough the projection system and immersion fluid that forms animmersion area adjacent to the projection system; a substrate stage thatholds the substrate and that moves the substrate; a detector thatdetects a portion of the substrate on which the immersion fluid remains;and a controller that moves the substrate stage based on detections madeby the detector to remove the immersion fluid from the portion of thesubstrate.
 42. The immersion lithography apparatus of claim 41, whereinthe substrate is moved relative to the immersion area based ondetections made by the detector so that the immersion fluid that remainson the substrate is engulfed by the immersion fluid of the immersionarea.
 43. The immersion lithography apparatus of claim 42, furthercomprising a fluid recovery system, and wherein the substrate is movedrelative to the fluid recovery system based on the detections made bythe detector so that the immersion fluid that remains on the portion ofthe substrate is removed through the fluid recovery system.
 44. Theimmersion lithography apparatus of claim 41, wherein the detector is anoptical detector.
 45. The immersion lithography apparatus of claim 44,wherein the detector is an auto-focus detector.
 46. The immersionlithography apparatus of claim 41, wherein a plurality of shot areas onthe substrate are exposed through the projection system, and thecontroller moves the substrate to remove the immersion fluid thatremains on the portion of the substrate at least once between a starttime when exposure of a first one of the shot areas on the substratebegins and an end time after the exposure of a last one of the shotareas on the substrate has been completed.
 47. The immersion lithographyapparatus of claim 46, wherein the controller performs an operation tomove the substrate to remove the immersion fluid that remains on theportion of the substrate multiple times between the start time and theend time.
 48. The immersion lithography apparatus of claim 46, whereinthe controller performs an operation to move the substrate to remove theimmersion fluid that remains on the portion of the substrate at leastafter the exposure of all the shot areas on the substrate has beencompleted.
 49. The immersion lithography apparatus of claim 41, whereinthe immersion lithography apparatus is a scanning exposure apparatus andthe controller moves the substrate relative to the immersion area in ascanning direction during the exposure of the substrate to theradiation.
 50. The immersion lithography apparatus of claim 41, whereinthe controller moves the substrate stage so as to remove immersion fluidthat remains on a portion of the surface of the substrate stage.
 51. Animmersion lithography apparatus comprising: a projection system thatexposes a substrate with radiation, the substrate being exposed with theradiation through the projection system and immersion fluid that formsan immersion area adjacent to the projection system; a substrate stagethat holds the substrate and that moves the substrate; and a controllerthat moves the substrate stage to remove the immersion fluid from aportion of the substrate, wherein the controller determines a path alongwhich the substrate is to be moved before moving the substrate to removethe immersion fluid that remains on the portion of the substrate, thepath being determined based upon previous movements of the substrate.52. The immersion lithography apparatus of claim 51, wherein the path isdetermined based upon at least one of a speed and a length of theprevious movements of the substrate.
 53. The immersion lithographyapparatus of claim 51, wherein the substrate is moved relative to theimmersion area based on the determined path so that the immersion fluidthat remains on the substrate is engulfed by the immersion fluid of theimmersion area.
 54. The immersion lithography apparatus of claim 53,further comprising a fluid recovery system, and wherein the substrate ismoved relative to the fluid recovery system based on the determined pathso that the immersion fluid that remains on the portion of the substrateis removed through the fluid recovery system.
 55. The immersionlithography apparatus of claim 51, wherein a plurality of shot areas onthe substrate are exposed through the projection system, and controllermoves the substrate to remove the immersion fluid that remains on theportion of the substrate at least once between a start time whenexposure of a first one of the shot areas on the substrate begins and anend time after the exposure of a last one of the shot areas on thesubstrate has been completed.
 56. The immersion lithography apparatus ofclaim 55, wherein the controller performs an operation to move thesubstrate to remove the immersion fluid that remains on the portion ofthe substrate multiple times between the start time and the end time.57. The immersion lithography apparatus of claim 55, wherein thecontroller performs an operation to move the substrate to remove theimmersion fluid that remains on the portion of the substrate at leastafter the exposure of all the shot areas on the substrate has beencompleted.
 58. The immersion lithography apparatus of claim 51, whereinthe immersion lithography apparatus is a scanning exposure apparatus andthe controller moves the substrate relative to the immersion area in ascanning direction during the exposure of the substrate to theradiation.
 59. The immersion lithography apparatus of claim 51, whereinthe controller moves the substrate stage so as to remove immersion fluidthat remains on a portion of the surface of the substrate stage.
 60. Adevice manufacturing method comprising: exposing a substrate by usingthe method of performing immersion lithography defined in claim 21; anddeveloping the exposed substrate.
 61. A device manufacturing methodcomprising: exposing a substrate by using the method of performingimmersion lithography defined in claim 31; and developing the exposedsubstrate.